Subject: | |
From: | |
Reply To: | |
Date: | Sat, 23 Oct 2004 20:36:35 -0400 |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
Jeff,
From what I understand about the 220/222MHZ band, it is divided into 5KHZ
channels. The mode that is used for voice communications is acsb (amplitude
commanded single sideband). Acsb is a standard ssb signal that is
compressed. There is also a pilot tone inserted 3.1khz out from the ssb
signal. This enables the receiver to frequency lock to the transmitted
signal. When a signal is received the signal is expanded and demodulated
like an ssb signal with the pilot notched out. When I lived in north Jersey
in the 1990s there was a large acssb trunked system in the new York metro
area. I haven't caught any 220/222 activity here in my present location of
southern Virginia. I hope this helps.
Dave Marthouse N2AAM
[log in to unmask]
----- Original Message -----
From: "Jeff Kenyon" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, October 23, 2004 5:58 PM
Subject: 220 MHz use and modes used and possible encryption?
> Hi everyone. I was just doing a casual search of the 220-222 MHz range
> here in my area, and I have a couple of trunked systems that are in my
> area that are listed for this band, and they are the MPT-1327 types of
> systems, and when I have searched there before I have heard control
> channels, and on one other occasion I have heard voice coms there, and
> today I also heard these coms. I first started to monitor in narrow band
> FM which is the default for my scanner, and then tried to monitor in wide
> band FM and AM with no luck. It appears as though they are either using
> SSB or some kind of analogue encryption. I am not sure if there is any
> conventional use or who else uses the 220-222 MHz band, but what I was
> wondering is what have others heard in the 220-222 MHz range in your area?
>
|
|
|